nested object forms

Question

I'm a rails and ruby noob, and Im pretty sure this something completely stupid I am missing..

Trying to build a nested form, and have found many examples online, and tried and failed to reproduce the desired result.

the "seller" fields are not even displayed, and when I submit form I get:

unknown attribute: item

models:

class Dealerform < ActiveRecord::Base
 belongs_to :dealer
 has_one :seller :class_name => 'Seller'
 has_many :items, :through => :seller
 accepts_nested_attributes_for :seller, :items

end

class Seller < ActiveRecord::Base
 belongs_to :dealerform
 has_many :items :class_name => 'Item'
end

class Item < ActiveRecord::Base
 belongs_to :seller
end

view:

<% form_for(@dealerform) do |f| %>
<%= f.error_messages %>
 <p>
 <%= f.label :date %><br />
 <%= f.datetime_select :date %>
 </p>
      #...more fields ...

<% f.fields_for :seller do |seller| %>

<p>
 <%= seller.label :fname %><br />
 <%= seller.text_field :fname %>
</p>
      #...more fields ...

<% end %>

 <% f.fields_for :item do |item| %>
  <p>
   <%= item.label :foo %><br />
   <%= item.text_field :foo %>
  </p>
      #...more fields ...

 <% end %>

<%= f.submit 'Create' %> 
<% end %>

Based on suggestions.. changed the following lines:

<% f.fields_for :seller do |seller| %>
<% f.fields_for :item do |item| %>

to:

<% f.fields_for @seller do |seller| %>
<% f.fields_for @item do |item| %>

and now they show up in the form, and when trying to submit form I get:

unknown attribute: nil_class

when I change:

def new
  @dealerform = Dealerform.new

to:

def new
  @dealerform = Dealerform.new
  @dealerform.seller.build

I get:

undefined method `build' for nil:NilClass

Hints: Please don't begin sentences with "so". Please begin sentences with Capital Letters. Please capitalize "I". — S.Lott
– S.Lott, Commented Oct 23, 2010 at 18:31
Reminder — if you're working in Rails 3.0.0 or 2.3.9, be sure to upgrade now, since there is a security vulnerability for accepts_nested_attributes_for. — Matchu
– Matchu, Commented Oct 23, 2010 at 18:33

Sam 山 · Accepted Answer · 2010-10-23 22:51:11Z

2

It's because the fields_for attribute wil only display resources that exist. In your controller you need to build objects for the forms to containe.

So in your controller

def new
    #2.times {@dealer_form.items}
    @dealer_form = DealerForm.new
    @dealer_form.seller = Seller.new
    #or @dealer_form.seller.build
end

edited Oct 23, 2010 at 22:51

answered Oct 23, 2010 at 18:31

Sam 山

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7 Comments

sysconfig Over a year ago

made this change and now get: undefined method `build' for nil:NilClass

Sam 山 Over a year ago

It just means that you are building something that doesn't exist.

Sam 山 Over a year ago

check your associations. You have too many for me to go over each and if I did I'm not sure you declared all of them correctly. Just make sure sellers is actually a has_many and so on... :)

Matchu Over a year ago

@Sam: this is the result I'd expect from @dealer_form.seller.build. If there is no seller defined yet, @dealer_form.seller will return nil, right? Or is there some Ruby duck typing there that I haven't dealt with before?

Sam 山 Over a year ago

I don't really know. Its sounds like you got more than a simple thing setup. Start with a really simple association and then move from there. As for the nil error your getting it just means that your associations are wrong.

|

njorden · Accepted Answer · 2010-10-23 18:40:32Z

0

It looks like your dealerform model has_many items but your fields_for is submitting a singular item, so when it tries to initialize your dealerform in the create action it's trying to assign dealerform.item but there's no such method. If a dealerform has many items you may want to check out this example http://media.pragprog.com/titles/fr_arr/multiple_models_one_form.pdf for how to manage the has_many in a single form.

answered Oct 23, 2010 at 18:40

njorden

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Comments

DGM · Accepted Answer · 2010-10-23 21:56:11Z

0

As Sam indicated, you ned to have an actual object, whether new or existing:

f.fields_for @seller

You can get @seller in several different ways, using build to create a new one, or if you are editing an existing record, use @dealerform.seller.

In the case of items, you may need to loop over several, depending on how many form you want to display. Check out http://www.railscasts.com for some screencasts on this.

answered Oct 23, 2010 at 21:56

DGM

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